1. Field of the Invention
The present invention relates to video switching apparatus for switching between a plurality of video signal inputs and outputting the selected video signal input to video recording apparatus or a monitor, and in particular to video switching apparatus for processing the video signal input of a plurality of channels multiplexed in time units such as frames and fields.
2. Description of the Related Art
Video switching apparatus called a frame switcher or a multiplexer has been in use for inputting a plurality of video signals such as video outputs from a plurality of video cameras and dividing per channel the signal in time units such as frames and fields to multiplex the signals and outputting the signals to video recording apparatus such as a VTR, or inputting a multiple video signal generated by video recording apparatus and outputting the signal per channel onto a monitor. Such video switching apparatus generally appends an ID signal for identification to the video signal on each channel for multiplexing and records these video signals as a single video signal on video recording apparatus. To generate a multiplexed video signal, the ID signal superimposed on a video signal is read, the target video signal is selected based on the ID information and the video signals on the established channels are extracted so that only the video signals where the same ID signal is superimposed are output to a monitor. By appending an ID signal, it is possible to select and output a video signal on a predetermined channel.
Specifications of such an ID signal are uniquely defined per manufacturer and type of apparatus. While a multiple video signal on which an ID signal conforming to the apparatus in use is superimposed can be selected and generated, a multiple video signal on which an ID signal of an unsupported system is superimposed does not allow generation of the signal on a predetermined channel or video switchover since corresponding ID information cannot be recognized.
In order to solve such a problem, apparatus has been proposed for appending an ID signal conforming to the same system as the apparatus in use in generating a multiple video signal recorded with an ID signal of a different system is superimposed in order to allow generation control such as signal switchover via the appended ID signal. A configuration example of video switching apparatus for appending a ID signal conforming to the apparatus in use in generating a multiple video signal conforming to a different system.
Video switching apparatus 51 is composed of an ID detecting circuit 52, an ID information read circuit 53, a play/recording control circuit 54, a selector for selecting video signals 55, an ID generation circuit 56, and a selector for selecting ID signals 57. To a generation input terminal 58 is connected the output terminal of video recording apparatus 62. To a recording output terminal 59 is connected the input terminal of the video recording apparatus 62. To a monitor output terminal 60 is connected a monitor 61.
The video switching apparatus 51 in this example is configured so that the generation mode may be set in advance on the menu setup section (not shown) by the user to input a setup mode signal. The case where a multiple video signal on which an ID signal conforming to the same system as the apparatus in use is superimposed is generated is called Mode A, while the case where a multiple video signal on which an ID signal of a different system is superimposed is generated is called Mode B.
For Mode A, the input of the selector 57 is connected to the generation input terminal 58. A video signal input from the generation input terminal 58 is input to the ID detecting circuit 52 and the ID information read circuit 53 via the selector 57. The ID detecting circuit 52 detects presence/absence of an ID signal in a video signal and outputs a switching control signal to the selector 55 depending on the detection result. In case the ID signal is detected (the ID signal is superimposed), the selector 55 outputs an output video signal S2 of the play/recording control circuit 54 to the monitor output terminal 60. In case the ID signal is not detected (the ID signal is not superimposed), the selector 55 outputs a video signal S1 input from the generation input terminal 58 to the monitor output terminal 60. The output video signal S2 of the play/recording control circuit 54 is also output to the recording output terminal 59.
The ID information read circuit 53 reads the information in the ID signal and outputs the ID information to the play/recording control circuit 54. The play/recording control circuit 54 processes the video signal based on the input ID information. For example, the play/recording control circuit 54 extracts and outputs only a video signal where the predetermined same ID information specified by the user is superimposed from a multiple video signal divided on channels per frame or field. In case no ID information is input, the play/recording control circuit 54 outputs a black image video signal.
For Mode B, the input of the selector 57 is connected to the ID generation circuit 56. A conforming ID signal generated in the ID generation circuit 56 is input to the ID detecting circuit 52 and the ID information read circuit 53 via the selector 57. The ID detecting circuit 52 detects the ID signal generated in the ID generation circuit 56 and outputs a switching control signal to the play/recording control circuit 54. The play/recording control circuit 54 outputs a video signal on a channel corresponding to the ID information from the multiple video signal. The video signal S2 is output to the monitor output terminal 60 via the selector 55. In this way, by generating and appending an ID system conforming to the system of the apparatus in use in generating a multiple video signal where an ID signal conforming to a different ID signal is superimposed, it is possible to control switchover of multiplexed video signals on channels.
The video switching apparatus 51 configured as mentioned earlier always appends a conforming ID signal to the input video signal S1 for generation in Mode B, so that the ID information in the appended ID signal is input to the play/recording control circuit 54 even when the video recording apparatus 62 has stopped generation. Thus, the channel corresponding to the ID information in the video signal S1 input from the generation input terminal 58 is output as a video signal S21 from the play/recording control circuit 54 and input to the video recording apparatus 62 from the recording output terminal 59.
The video recording apparatus 62 outputs (performs through output of) a signal input to the input terminal while it is not generating a video signal. When a video signal (actually noise component only) is input to the input terminal from the video switching apparatus 51 while generation by the video recording apparatus 62 is halted, the input video signal is output from the output terminal then input to the generation input terminal 58 of the video switching apparatus 51. That is, when generation operation is halted in the video recording apparatus 62 while the video switching apparatus 51 is operating in Mode B, a so-called signal path loop is formed thus causing failure such as oscillation.
The invention has been proposed in view of the aforementioned circumstances and aims at providing video switching apparatus that can generate a multiple video signal where an ID signal conforming to a system different from that employed by the apparatus in use is superimposed, and that can prevent failure such as oscillation in the generation mode according to the different system.
In order to solve such a problem, the first aspect of the invention is video switching apparatus for performing switchover to generate a video switching apparatus multiplexed on a plurality of channels, comprising ID detection means for detecting an ID signal for a channel-identification superimposed on said video signal, said ID signal including at least any one of a unique ID signal which conforms to the video switching apparatus or a non-unique ID signal which does not conform to the video switching apparatus; ID signal generation means for generating said unique ID signal; state determination means for determining an operating state based on a detection result obtained by said ID detection means and a specific operation mode; ID selection means for selecting the unique ID signal generated by said ID signal generation means based on a determination result by said state determination means, wherein said determination result is such that the specific operating mode is to generate the video signal where said non-unique ID signal is superimposed thereon when an ID signal is detected in a video signal by said ID detection means, and video signal switching control means for switching over said video signal based on ID information in the ID signal selected by said ID selection means. The second aspect of the invention is video switching apparatus characterized in that the ID detection means preferably detects presence/absence of a unique or non-unique ID signals superimposed ID signal in the vertical blanking period of the video signal.
The third aspect of the invention is video switching apparatus characterized in that the video signal switching control means preferably outputs a black image or a blue image in case an ID signal is not detected in the video signal.
The fourth aspect of the invention is video switching apparatus for performing switchover to generate a video switching apparatus multiplexed on a plurality of channels, characterized in that the apparatus comprises video halt detection means for detecting halt or continuation of the video signal, ID signal generation means for generating a unique ID signal conforming to the apparatus, state determination means for determining the operating state via the detection result by the video halt detection means and the specified operation mode, ID selection means for selecting the conforming ID signal generated by the ID signal generation means based on the determination result by the state determination means in a mode for generating a video signal where a non-unique ID signal is superimposed and only in case it is detected that a video signal is continued by the video halt detection means, and video signal switching control means for switching over the image signal via ID information in the ID signal selected by the ID selection means.
The fifth aspect of the invention is video switching apparatus characterized in that the video halt detection means preferably detects halt or continuation of the video signal via the state of an ID signal or a synchronization signal.
The sixth aspect of the invention is video switching apparatus characterized in that the video signal switching control means preferably outputs a black image or a blue image in case it has detected halt of the video signal.
In the aforementioned configuration, presence/absence of an ID signal is detected halt/continuation of a video signal is detected via a synchronization signal for the video signal. Then, a conforming ID signal is appended to switch over a video signal in a mode for generating a video signal where a nonconforming ID signal is superimposed and only in case an ID signal is detected in a video signal. Via this configuration, it is possible to generate as required a predetermined channel for a multiple video signal where a nonconforming ID signal is superimposed.
In a mode for generating a video signal where a nonconforming ID signal is superimposed and in case an ID signal cannot be detected or halt state of a video signal is detected, operation is controlled not to append a conforming ID signal and to switch over a video signal. Via this configuration, a black image or a blue image is output from video recording apparatus in case video generation by video recording apparatus for generating a video signal is halted and an input signal is output through the output terminal. Thus a signal path loop is not formed across video switching apparatus and video recording apparatus thereby preventing abnormal operation such as oscillation.